an unknown compound is known to contain 30.34%N and 60.56%O and has a molar mass of 92.00g. what are the empirical formula and the molecular formula for the compound?( O=16.0g/mol,N=14.1g/mol)
So what is the other 9 percent of the unknown compound?
I think we should add up nitrogen and oxygen. Then subtract the result from 100 percent. What do you think
To find the empirical formula and molecular formula for the compound, we need to determine the ratio of atoms in the compound. Here's how to calculate it:
1. Assume we have a 100g sample of the compound. This assumption allows us to work with percentages as grams.
2. Convert the given percentages into grams:
- Nitrogen (N): 30.34% of 100g = 30.34g
- Oxygen (O): 60.56% of 100g = 60.56g
3. Determine the number of moles of each element using their molar masses:
- Moles of N: 30.34g / 14.1g/mol = 2.16 mol
- Moles of O: 60.56g / 16.0g/mol = 3.78 mol
4. Divide the moles of each element by the smallest number of moles to obtain the simplest (empirical) ratio:
- N: 2.16 mol / 2.16 mol = 1
- O: 3.78 mol / 2.16 mol ≈ 1.75
We have approximately N1O1.75 as the empirical formula. However, we need to find whole-number subscripts, so multiply the ratio by 4 (the smallest number that gives us whole-numbers):
- N1 * 4 = N4
- O1.75 * 4 = O7
Therefore, the empirical formula for the compound is N4O7.
Next, to find the molecular formula, we need to know the molar mass of the compound. In this case, the molar mass is 92.00g.
5. Calculate the empirical formula mass:
- N4O7:
- Nitrogen: 4 * 14.1g/mol = 56.4g/mol
- Oxygen: 7 * 16.0g/mol = 112g/mol
- Empirical Formula Mass: 56.4g/mol + 112g/mol = 168.4g/mol
6. Determine the factor by which the empirical formula mass must be multiplied to match the molar mass of the compound:
- Factor = 92.00g/mol / 168.4g/mol ≈ 0.546
7. Multiply the subscripts in the empirical formula by the factor obtained:
- N4 * 0.546 ≈ N2
- O7 * 0.546 ≈ O3.82
Round the subscripts to the nearest whole number (keep in mind the rounding errors) to obtain the molecular formula:
- Molecular formula ≈ N2O4
Therefore, the empirical formula for the compound is N4O7, and the molecular formula is approximately N2O4.